Anonymous data is one identifier or clever match away from identification. This is particularly severe for sites/services/hardware that records audio (man, who would knowingly allow that kind of abuse??), but it can apply to mouse tracking too. Mouse tracking fingerprints could be used to re-identify all sorts of other things.

For some people, there is no difference ultimately. Because it's not that they aren't doing anything malicious with the collected data now, it's about the fact that they CAN do it if they desire to (ethical or not) in the future--the data is being collected, stored (perhaps indefinitely), and will always be accessible. In a world where capitalism reigns, to think that any large corporate business would treat our data with the best care and in our bests interests seems a little silly. I have always held the belief that businesses are not people and it's reasonable to expect that businesses may not be inclined to always do the right thing, especially if it gains them more money and power.

There is no such thing as anonymous data. The belief that something is anonymous is simply an aspect of statistical ignorance or naiveté.

And, since we can't know in advance all the ways data can be combined, recombined, projected, and analyzed there is no such thing as informed consent to use said data unless specifically restricted to a single analysis using only given data.